1. Field of the Invention
The present invention relates to an endoscope including an objective optical system which guides an observation image to an image pickup element while varying a direction of guide by a prism.
2. Description of the Related Art
Jpn. Pat. Appln. KOKAI Publication No. H09-149883, for instance, discloses a side-viewing electronic endoscope which can exactly and easily dispose an optical axis of an objective optical system. In this side-viewing electronic endoscope, the objective optical system including a prism is precisely composed of two units by two frame members. Further, the two units are assembled by using position restriction means which comprises an engaging groove and a projection portion, whereby rotation about the axis is restricted (corresponding restriction in an up-and-down direction and restriction in a right-and-left direction) and back-and-forth movement in the axial direction is restricted (focus position adjustment). Thereby, in the side-viewing electronic endoscope, the optical axis is exactly and easily disposed in the normal position, and the optical performance is ensured.